Test systems are configured to test the operation of electronic devices, such as microprocessors and memory chips, Testing may include sending signals to a device and determining how the device reacted to those signals based on its response. For example, testing may include sending test signals to a device, such as an integrated circuit (IC), and receiving radio frequency (RF) signals back from the device. The RF signals are processed to determine whether the device is performing acceptably. An error vector magnitude (EVM) is a measure of signal quality in the test system.